High-dose vitamin E supplementation normalizes retinal blood flow and creatinine clearance in patients with type 1 diabetes

OBJECTIVE - To determine the effectiveness of vitamin E treatment in normalizing retinal blood flow and renal function in patients with <10 years of type 1 diabetes. RESEARCH DESIGN AND METHODS - An 8-month randomized double-masked placebo-controlled crossover trial evaluated 36 type 1 diabetic and 9 nondiabetic subjects. Subjects were randomly assigned to either 1,800 IU vitamin E/day or placebo for 4- months and followed, after treatment crossover, for a further 4 months. Retinal blood flow was measured using video fluorescein angiography, and renal function was assessed using normalized creatinine clearance from timed urine collections. RESULTS - After vitamin E treatment, serum levels of vitamin E were significantly elevated (P < 0.01) in both type 1 diabetic and control patients. Hemoglobin Al, was not affected by vitamin E treatment. Diabetic patient baseline retinal blood flow (29.1 +/- 7.5 pixel(2)/s) was significantly (P = 0.030) decreased compared with that of nondiabetic subjects (35.2 +/- 7.2 pixel(2)/s). After vitamin E treatment, diabetic patient retinal blood flow (34.5 +/- 7.8 pixel(2)/s) was significantly increased (P < 0.001) and was comparable with that of nondiabetic subjects. Additionally, vitamin E treatment significantly (P = 0.039) normalized elevated baseline creatinine clearance in diabetic patients. CONCLUSIONS - Oral vitamin E treatment appears to be effective in normalizing retinal hemodynamic abnormalities and improving renal function in type 1 diabetic patients of short disease duration without inducing a significant change in glycemic control. This suggests that vitamin E supplementation may provide an additional benefit in reducing the risks for developing diabetic retinopathy or nephropathy.